CD44 and posterior cortical atrophy: Therefore, to further dissect the PCa cell heterogeneity, in this part of the project, we employed both surface markers (CD44, α2β1, and, for comparison, ABCG2) and functional (i.e., SP and Aldefluor) assays to dissect the tumorigenicity of PCa cell subpopulations in three PSA− (Du145, PPC-1 and PC3; all three models do not express AR and PSA and contain only PSA− cells) and three PSA+ (LNCaP, LAPC4 and LAPC9; all 3 models contain PSA+ and PSA−/lo cells) PCa models.